Prior patents for spirit levels, lighted or unlighted are as follows:
All levels including the following U.S. Pat. Nos. 4,685,219, 3,738,015, 794,753 and 94850, disclose a method of securing a bubble vial in a wood or metal beam with natural light for reading of the vial provided by a port hole type aperture.
U.S. Pat. Nos. 794,753, 948,570, 1,566,541, 2,607,882, 2,806,133 and 4,407,075 are illuminated levels which use various batteries, bulbs and wires to light up, reflect, direct or bounce the light off the bubble vials that are secured in a beam that is described previously.
No provision is made for easy manufacture, installation or quick servicing of the lighted devices.
U.S. Pat. No. 4,654,977 shows an electronic level that has no liquid bubble vial.